US2390183A - Stamping die - Google Patents

Description

Dec. 4, 1945. R. A. L. SELIGMAN STAMPING DIE Filed Dec. 6, 1940 l l l l l \\\l Patented Dec. 4, 1945 STAMPIN G DIE Roger Adolphe Leonard Selig-man, Paris, France; vested in the Alien Property Custodian Application December 6, 1940, Serial No. 368,873

15 Claims.

This invention relates to a method of making stamping dies, more particularly dies used in the stamping of sheet metal forms of any kind, large o-r small, and to the novel stamping die so made.

It has long been known that the making of dies for sheet metal stamping, particularly in the larger sizes, is a long and tedious task. rIhe metal of which the die is to be made must be exceedingly hard, and accordingly, requires the use of cutting tools of even greater hardness, for example tungsten carbide, in order to machine the same. Often, in the case of deeply recessed dies, a co-mparatively large amount of metal must be removed in the machining operation, and the task of establishing the desired surface, and producing thereon the requisite smoothness or polish, is exacting work and is both expensive and timeconsuming. An important part of the expense .and delay in the manufacture of new styles of automobile bodies, duralumin plates for the airfoil surfaces of airplane wings, and the like, is attributable to the time and expense necessary in machining the dies between which such shapes are stamped from sheet stock.

The object of the present invention is to enable stamping dies to be made cheaply and comparatively rapidly having a hardened Working surface of any desired configuration and substantial hardness at least in that part of the backing ma.. terial which lies immediately behind the hardened working face.

According to one form of the present invention, one cr more steel sheets of a suitable thickness and having at least one face sufficiently smooth to serve as the working face of the required die, are bent or welded or otherwise joined together to the desired shape and temporarily secured in that shape by any suitable means such, for example, as by pouring a temporary concrete form against its smooth face. Thereafter the space behind the plate, which is to constitute the body portion of the die, is built up with a mixture of metallic particles or fragments, said mixture comprising at least one metal or metallic alloy whose melting point is not higher than the temperature at which hardening of the steel face plate can be accomplished (having regard to the particular character of the steel of which the face plate is made), and then compressing together the face plate and the mixture of solid particles behind it at that temperature which will melt the metallic component of the mixture behind the face plate causing said mixture to become fluid while said temperature is maintained, said temperature being also that which will accomplish a hardening of the face plate. Thereafter the mass is 'cooled in whatever manner is most appropriate to secure and maintain the maximum degree of hardness of the face plate and such cooling solidifies the previously Huid mass in the backing portion into a solid metallic mass. The cement or concrete which serves as a temporary form may be removed before or after cooling, as desired, andthe die, after such incidental dressing as may be necessary, is ready for use.

Referring to the drawing annexed to and forming a part of this specification- Fig. l is a cross section of a female die having a concave working surface, as now in common use, machined out of a single block of hardened steel.

Fig. 2 shows in cross section a steel plate bent so that its concave face corresponds exactly to the shape of the concave working face of the die shown in Fig. 1.

Fig. 3 shows in cross section the said plate mounted upon a temporary concrete form with its working face positioned against the concrete, and with temporary side wall members adapted to retain a mass of backing material or fragments thereafter to be placed in position against the back of the plate.

Fig. 4 shows in somewhat larger scale and partly in section and partly in side elevation the space behind the facing plate filled with a mixture of solid particles, hereinafter more particularly described.

Figs. 5 and 6 are similar to Fig. 4, but differ therefrom in showing different materials used for filling in the space behind the plate as hereinafter set forth. i

Fig. 7 shows in cross section a finished stamping die made according to this invention.

Figs. 8 and 9 show in still further enlarged scale and in cross section various means which may be used to improve the adherence between the face plate and the backing material, as hereinafter described.

Referring to the drawing, wherein like reference characters refer to like parts- In Fig. 1 there is shown a form of female stamping die which might be used, for example, in shaping a duralumin plate for a part of an airplane wing. Such die is employed in a heavy press and in conjunction with a male die of complementary shape. The particular shape shown has been selected merely for illustration and it will be understood that the invention applies equally to the making of the complementary male die. While the invention here described applies to the making of a stamping die of any desired face shape which can be achieved by the bending or Working of a thin plate of steel or equivalent metal, the invention will be here described in connection with the manufacture of a die similar to that shown in Fig. 1.

According to the present invention, a sheet of steel or other equivalent hard metal of relatively high melting point which is not too brittle to be bent to thev desired shape andy which has a critical temperature of hardenin-g Within a suitable range, is lbent in such manner that one of its faces is madeto assume the desired conguration of the die to be made. The thickness. of the plate is not of critical importance so long as it may be bent or Worked to the desired configuration. For purposes of illustration, a plate l cm. in thickness maybe used. Referring to Figs. 2 to 7, inclusive, a sheet of steel I0 having one face thereof sufliciently smooth to serve as the Work-ing face oi the die, is bent. to the re.- qllQd Shape. The.. Working face IIY thereofY is preier'ably a polished surface, and it is one of `the advantages of thisv invention that the polish can be givenY toA this surface. ofthe. plate before bending andlwhile the same is at. The opposite face t2'of the plate, I shouldpreferably not be polished. It may 1de left as it comes from. the rolluirlgy millor it, may` be artificially roughened in any desired manner to improve. capacity to bond with the backingrloatorial` Onomothodf of such roughening may, be, tov score, grooves. I3 therein (ses Figure 8) by the. ooo 0f anys-miam@ Shar tool;y another may be to cut grooves` I4. th` ein. having` undercut e'dgres- (see. Figure.` 9).; other methods of rougheninlg the surface in or.- der. to. improve the; quality of; the bono may. be employed.

Hate. llt. after, havinglooen bon-.tto the desired shape, is then temporarily supported in thaty shape upon aform of poured Concrete or Cement |15; containedI inV a.. suitable., mold I6, The concrete is allowed tov harden inV GQIl'GaC. With; the

smooth4 Working face I;I of the plate/and care;

is taken thatthe` concrete: is. s-uicientlyY in,y con.- tact with. the plate. so that. deformation of, the latter does not occur in subsequentstages ofthe process. I f desired; hard; dry sand; may be used Where it issupported in a mold in such mannerv asr ton withstand.` sufficiently.- the. pressures involvedi The concrete form is made With side Walls; ISI: prog-eating; upwardly to a suitable height at; the edges of' the plate, forming a continuous vvall surrounding the plate. and' defini-ng the. edges thereof, and forming a space I8 which is after-- Wards to be lled With backing material.. If: desired edge-facing plates of` steel-v |19l may be. in: serted tol define` the marginal boundaries of. the space I8f.

Within `the space I8' is placed a material.; or a mixture ot materials, which when properly hardened in place will afford a` suitable. backingfor theface-` plate1 Il); Such material may be either a metal or analloy ofi metals ora mixture of differentmetalsl or` ofdifferentalloys, one of these beingherein referred toas the fusing'fcomponent. Alt; least= one of thev metalsl or alloyspresent is the fusing componentgand this shouldA be capable of melting atatemperature not higher than the highestI temperature to which the face plate I0 can be raisedin thecourse of'.v hardening of-its surfacebyv heat treatment. For example, iffthe face plateI- beef steeliwhic-h'. hardens byquenehing afterV being heated to about 810 C.,

. tinuous metallic matrixvv' there may be used as the fusing component of the material placed in space I8 a metal or an alloy which has a melting point below 810 C. On the other hand, the steel mentioned may be safely heated to temperatures substantially higher than 810 C. and hardness may be attained by quenching from above that ligure if the stages of cooling from the highest temperature to about 810 are very gradual, as is Well known. Thus, there may be used, as the fusing component of the backing material placed in space I8, alloys e Whose melting points are substantially higher than 810 C., but in such cases the subsequent stages of cooling must be carried out in such manner as to retain the desired hardness of the s/teel'facing plate. The fusing component should, preferably, be an alloy of aluminum or copper having a melting point substantially less-than 1000,o C.

Example' 1.-If the face plate is a steel having al critical temperature, of, crystalline conversion about '750.D C., thef material placed in the,u space I8i may consist of a n-iixture of iron or steel. frag ments andY powdered, duralumin the proportions of approximately 90% byy Weigh-htr of, iron particles and 10% byf weight, ofv duralumin the form of; annely divided powder.. Ii theI dufalumn usedhas; the Composition or about 4%. Conner... 0.5% magnesium., 0J? %,v manganese.. and: the, rest aluminum, than: the molt'zrlgnoint. thereof; Will: be about. 655 C.: Accotdlrflely.,` upon the Subsequent. heaviest the temperature; should be.- brousht to; about '15.0'- G. and atthis temperature the duraluminnowdcrrwill; e1t;and.form=.a.oon-

n the space.. |18. con.- taining` in suspension i1 fragments- Wh-ioh-l at: the telfnperatureA indicated, vv-illg,V of` course,v not melt. Subsequent quenching from this temnerature is. thenA carried outv in.. Such manneras; to. bring about the. desired hardening of; the: face. plate Ill).

Emamplee2i;.-Iftheacef plate luisa steel Whose. maximum. hardnesscan be; achieved.r and; not. 10st` by elevation of the temperature: t'o.925fLVA Cg. pro:` vided the.y temperature is. then; reduced; slowlyl and Withouttoo. rapid? cooling.- toabout 810'? C., then the.. material` placed in; the space t8 may; consist;v of; a mixture of iron fragments with; finely. pow;- de-red aluminum bronze alloy in. about.. the pro., portionspreviously stated. Preferably that form of aluminum bronze alloy is used'l which'. isknown as A No. l.,consisting of` 89%,copper'ands11% aluminum, and. has a melting.v point..offabout;.925?" C. The use of aluminum. bronze alloy.-

sug-

gested becausey upon soliidifSyi-ng. this.. alloy.y isy en ceedingly tough andi resistant. to.= compression. When using thealuminum bronze-alloy,` the ma`v terial' is thenheated? to'- a temperature which. is: highenough` tomelt the powderedi alloy andlto cause the material Withinv space-` I8- .to fuse,v sothat the alloy becomes a matrix of' continuousv phase. BecauseA of the necessity ofcarrying;the. temperature ofheatingftoabout 925 C'.,.in= order to fuse the alloy; it thenlloecornes` neoessaryrini order that i the 'plate I- shall'.v regain its4 hardness', toc0011 the mass` in` the. manner. welll' undenstllor):v in the art.. off hardening steell plates..

alloy mentioned. in the preceding: example, there.

may beu'sedl'- an alloy of aluminum orcopper. or.; both l with added metallic. arsenicory silicon. Such. an alloy, dependingl on the percentage of; arsenic: orf-silicon present, Willi have a: linear' coeicientof'.- expansion more,e nearly.v equa-l1 to: thatt of steel.. Thus,- by using. analloy containing a desired' pers.

centage of a metal having the eiect of reducing the linear coefficient of expansion, the fusing component of the backing material will contract in cooling substantially or sufficiently equally to the contraction of the steel facing plate, thus reducing the possibility of deformation of the facing plate due to unequal contraction during cooling.

Example 4.--The material placed in space i8 may comprise a mixture of the low-melting alloy, such, for instance, as one of the alloys mentioned in the previous examples, with fragments of any hard material, metallic or non-metallic, having a substantially higher melting point. The size of these fragments may vary within wide limits fromV particles that will pass through f a comparatively fine mesh screen to large fragments or blocks, as set forth in Example 5 below. Preferably, fragments of iron or steel are used because it is not necessary that allgthe material introduced into space I8 shall melt and because at the temperatures used the iron fragments will tend to harden and anneal, but any other hard material or alloy, or any hard nonmetallic substance of sufficient resistance to deformation by crushing, may be used. According to one form of this invention, these fragments may be of graduated size, as indicated in Fig. 5, with the smaller fragments preferably positioned in closest proximity to plate l and the coarser fragments further removed therefrom. In this way, particularly where using a low-melting alloy of metal which in itself is not as hard as may be desired, greater resistance to deformation may be obtained within the area close behind the face plate l0.

Example Within the space I8 may be inserted a block of cast iron, roughly but not accuratelir cut to the approximate internal shape of the space I8. Through this block may be drilled holes 2l, penetrating the same from top to bottom. This form of the invention may be regarded as the limit case in which the material of high melting point, instead of being introduced in the form of many small fragments or a smaller number of large fragments, is now introduced in the form of a single large fragment or block. In this example-the metal or alloy of relatively low melting point may be sprinkled upon the surface l2 of the plate before the block 20 is put in position and in addition introduced in powder form through the holes 2l and inserted around the edges.

Eample 6.-The material with which the space I8 is filled may be introduced in molten form at a temperature not in excess of the temperature to which the steel plate l can be heated in the course of hardening. In such case the molten metal added may consist wholly of a metal or alloy which melts at or below that temperature, such as one of the alloys mentioned in Examples l, 2 or 3, or it may consist of such metal or alloy in molten form carrying in suspension fragments of solid matter such as fragments of iron, which are solid at that temperature, or such alloy or metal in molten form may be poured upon a mass of solid fragments filling the space I8 and preferably after such particles have been heated so that the added molten metal will remain in uid form until it has fully penetrated the interstices between the fragments, especially in the area adjacent plate I0, or such molten alloy or metal may be fed under pressure through hole 2l in a solid block of metal 20, in Which case one or more of the holes 2l may be used for the feeding of the hot metal and the other holes 2l may be lled with sand to permit escape of the displaced air.

Where in any of the foregoing examples it is proposed to use a mixture of metallic fragments with a metal of lower melting point, it will be understood that no substantial alloying of the two metals will occur at the temperatures employed and that in the finished die the two metals exist separately without a substantial degree of amalgamation.`

After the space I8 has been filled in any one of the manners suggested, the plate and its backing are then heated to, or maintained at, a temperature which is sumcient to assure proper fusing of the alloy or metal in the space I8 which has the relatively low melting point, and such temperature is maintained until space IB has been solidly filled (and air is suiiciently eliminated) to such depth as to assure adequate and solid backing for the plate l0.

If desired, before the heating, or during the early stages of cooling, or both, the mass of material within space I8 may be compressed in any suitable manner. For example, the mold I6 with all of its contents may be placed in a press anda flat stamping die may then beibrought down into Contact with the upper surface of the materialn in space i8 and the whole may then be placed under substantial pressure in order to homogenize the material within space 8.

While the temperature is maintained the mass of backing material bonds sufciently to the plate If! so that the same will be rmly held when the die is cool.

After cooling, the temporary mold IE and the temporary concrete form I5 are cut away. The result is a stamping die as shown in Fig. 7, having the desired shape in its working face and being of compound structure comprising the steel plate l) and the hardened backing material 22 consisting of a homogeneous mass having a continuous metallic phase and preferably containing one or more fragments of hard material having a melting point substantially higher than the temperatures at which the die was formed.

Accordingly, the process of this invention is adapted to accomplish simultaneously (a) the formation of a hard homogeneous metallic mass behind the working face 0f thedie and supporting the same, and (b) the hardening of the steel plate forming the working face of the die, both results being accomplished in a single stage of treatment by reasony of the relationship between the melting point of the fluXing metal and the critical temperature of molecular rearrangement of the plate which forms the working face of the die, and the product of this invention is the article so made.

Certain types of steels which may be used for the facing plate of this invention may require or permit the hardening thereof by successive steps of heating, quenching, aging, reheating, gradual cooling, and the like, as is well understood in the art. It may be desirable when using certain steels, to perform some but not all of these steps before the backing material is applied to the plate. In that case, it will be understood that the remaining steps by which the desired hardness of the plate is secured or maintained may be carried out after the backing material has been applied in accordance with this invention.

I claim:

l. The method of making a shaped stamping die having a hardened Steel working face which includes forming? a' steel plate to' therv desired face; shapeg. filling the space'- adjacent the back of said plate with backing material composed in party at l'e'ast of a. metallic fusing component Whosel melting` point is not. higher thani the highest temper# atinie' to which the steel of the'plate may bera'ised Without detriment; to-y the subsequenthardening of said-.steel by quenching, heating` said backing ma-4 terialand steel plateto a temperature high enough tol melt the fusing component but'not higher'than the highest temperature to which. the steel can be raisedwithou-t detriment to the subsequent hardening thereof. by quenching, and. thenV Cooling. the backingmaterial. and steel plate together such' manner includ-ing quenching as to harden the pleite'.-

2.4 The method of making a shaped stamping dieA havingJ av hardened steell Working. facewhich includes forming afsteel' plate tothe desired face shape, compressing. against the back. of said plate a mass of particles including inpowderedv forma metal-Whosemelting point is notV higher than the highest temperature to which. thev steel of the plate may be raised Without-detriment to the sub-` sequent ha-rdening-v .0f said steel by quenching,

heating said mass of particles and. the steel pla-te to a temperature high. enough to melt the said gpowdered metal but not higher than the highest temperature-to Which the steel can` be raisefiwithout detriment-t0V the subsequent hardening thereof by quenching, and then cooling the. said mass andl the' said steel plate together in such manner including quenching. as to harden the plate.

3. The method of making a shapedl stamping die having a hardened steel Working. face which ing4 point not higher` than the highest temperature to which the steel o-f the plate may be raised` withoutv detriment to they subsequent hardening of saidsteel by quenching, said alloy also including af metal selected from the` group comprising arsenic' and silicon suicient to cause saidv backing material to possess a coeiiicientof linear expansionapproximately equal to that of. the steel in said plate, heating said backing material and steel plate to a temperature high enough to meltv said alloy but not higher than the highest temperature to which the steel canibe raised without-detri ment to the subsequent harden-ingthereofby quenching, and then cooling the` back-ing inateria-l and steelplate together in suchmanne-r including quenching asto harden the plate.. i

4. A shapedstamping die` having a facing element of steelhardened by quenching from-atemperatu-re not lessthan its temperature of crystalline conversion and a backing element bonded` to the facing` element, said back-.ing-elementcontaining. sufficient duralurnin. to endow the backing element with. a coefficient of expansion. similar tothat of the steel facing element.v

5. A shaped.' stamping. die having a; facing ele. ment-of steel-hardened by quenching from atem- .perature not less than its temperature of/crystalline conversion and; a backing elementbonded. to the facingv element,v said backing. element containing sufficient aluminum-bronze alloy .to endow the backing element. with accecient ofexpansion similar tofthat of. the steelfacing element.

6. A shaped stamping die having. a facing element of hardened steel and a backing element bonded tothe facing element, said backing elementbeing resistant to deformation under heavy pressure and being; composed at least part of an: alloyy containing sufcientarsenic toy impart to the backing element a coeicient of linear ex-` pansi'orr approximately equal: t'o that of the steelw in: the facing el'err-rent.`

A4 shaped: stamping dier having' a facing ele: ment ofhardened steelv and a backing. element-` bonded to the facing element, said backing cle-'-v nient-being resistant todeformation under heavy pressure and being composedat least in. partv of an.' alloy' containing. sufficient silicon to imp'alt to the .ba-cking elementl a coeflicient of linear expansionapproximately equal to that of the steell inf the facing element;-

8?. A stamping die comprising a facing element of steel hardened by quenching from'- a` tempera-- turez not less than its temperature of crystalline conversion and a metallic'backing element bond-` ed to the facing. element, said backing element consisting' of a mass composed principally of vhard metal' material resistant to deformation. under heavy pressure` and non-fusible at the saidV temperature and fusiblemetal bonding the back-'- ing element` through having been fused thereon on the facing element' at a temperature not high-v er than` the temperature of crystalline conversioni of the steel facing element,` said hardl metal materi'al and said fusible metal being present in proportions endowing said backing element with a coeiii'cient of linear expansion similar to that of the steel. facing element.

9; A stamping diecomprising a relatively thin' steel. plate having ay hardened working face and. a compressionresistant non-steely metallic` backf-A ing.' fused thereon, said metallic backing consiste ing of a mass of hard relatively non-fusiblefnetal having substantially theA same c'oefcient of. expansiorr as the' steel plate and high compression strength, said massv further containing other metall fused at a .temperature not higher than the temperaturey of crystalline conversion ofthe` steel` plate conditioning hardening' of the steel: plate by quenching, in a manner effecting co-Aw herence in the mass and fusion thereof to thesteel plate.

l0. A stamping die according to claim 8 wheres in said fusible metal comprises duralumin..

1l. A- starnping die according to claim 8v where-- in= said fusible metal comprises aluminum bronze alloy;

1121. A shaped stamping die having a facing element of steel hardened by quenching.. from a-tem-V perature not less than its temperature' of crystal; line conversion and a; backing element bonded to the iacinig element, said backing element being composed ofmaterial resistant to deformationun'der' heavy .pressure and containingv metalV and having a' melting. point not higher than the' highest temperature: to which the. steel of the facing` element may be raised. Without detriment to' the' subsequent hardening of the.' steel by quenching. sufficient of the metal being. present to endowf theA material of the' backing element with a cow ef'cient of expansion similar toY thatofgthe4 steel i facing element..

1'3. In a stamping die; a shaped facing, element of hardened steel and a backing element on the? facing element consisting. ofl a formed body of. :materiali resistant toA deformation under high pressure, Said material comprising pieces of ir'o'n' relatively infusible atv .the temperature of crystalline conversion of the. steel of the facing lele-` ment. andf other relatively hard metal fusible` at a'. temperature' not higher than said temperature*- off crystalline" conversi'on,. said other' metal fusing the pieces 0f iron together and fusing said body to the facing element and endowing said backing element with a coecient cf expansion similar to that of the steel of the facing element.

i4. In a stamping die, a shaped facing element of hardened steel and a backing element on the facing element consisting of a formed body of material resistant to deformation under heavy pressure, said material comprising pieces of steel relatively infusible at the temperature of Crystalline conversion of the steel of the facing element, and other relatively hard metal fusible at a temperature not higher than said temperature of crystalline conversion, said other metal fusing the pieces of steel together and to the backing element and endowing said backing element with a coefficient of expansion similar to that of the facing element.

15. In a stamping die, a shaped facing element of hardened steel and a backing element on the facing element consisting of a block of iron resistant to deformation under heavy pressure, and infusible at the temperature of crystalline conversion of the steel of the facing element, said block being provided with perforations extending therethrough, and other relatively hard metal fusible at a temperature not higher than the temperature of crystalline conversion of the steel of the facing element, said other metal being fused in and at least partially filling said perforations in contact With said facing element and fusing said block to the facing element and endowing said backing element with a coefficient of expansion'similar to that of the facing element.

ROGER ADOLPHE LEONARD SELIGMAN.

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